The present invention relates to an image pick-up lens which is preferable as an optical system of a solid-state imaging element such as a CCD type image sensor or a CMOS type image sensor, an image pick-up unit having the image pick-up lens, and a mobile terminal provided with this image pick-up unit.
Recently, following the technical advantages-offering, and size reduction of an image pick-up device using the solid-state imaging element such as CCD (Charged Coupled Device)type image sensor or CMOS (Complementary Metal Oxide Semiconductor)type image sensor, a cell phone or a personal computer, provided with the image pick-up device, is spreading.
Then, following an increase of the high density by the size reduction of these cell phone or personal computer, or an increase of functions, a request for more size reduction of the image pick-up lens mounted on the image pick-up device is emphasized to intend the size reduction of these image pick-up devices.
As such an image pick-up lens for a small size image pick-up device, an image pick-up lens of 3-lens composition in which, in an order from the object side, the first lens having the positive refractive power, the second lens having the negative refractive power, and the third lens having the positive refractive power are arranged, recently becomes common, from the reason why technical advantages can be more easily offered than one or 2-lens composition image pick-up lens. Such an image pick-up lens, so-called a triplet type image pick-up lens, is disclosed in the patent document 1.
[Patent Document 1]
Tokkai No. 2001-75006.
However, although an image pick-up lens of a type which is written in Patent Document 1, is a type in which a wide image angle is secured and aberrations are finely corrected, on the one hand, it is not suitable for a size reduction of the whole length of the image pick-up lens (a distance from the most object side surface of the whole image pick-up lens system to the image side focal point).